Novel Architecture of Indoor Bifacial Dye‐Sensitized Solar Cells with Efficiencies Surpassing 25% and Efficiency Ratios Exceeding 95%

Abstract

Regarding the light-to-energy conversion efficiency, it has been known to be controlled mainly by several components including the TiO 2 film, the dye, the electrolyte, and the counter electrodes. In the past few decades, a vast effort has been dedicated to the development of related components, seeking to increase the conversion efficiency of DSSCs. However, after these studies, the conversion efficiency under one sun illumination only increased a little bit from about 11% to 14%. [2][3][4][5] Recently, the applications of DSSC on dim light environments has drawn more and more attention, which is due to not only the slow progress in achieving satisfactory efficiency under sun-light illumination, but also the high efficiency achieved under the indoor light environment. [6] Furthermore, due to the rapid growth of the Internet of Things (IoT), more and more attention has been paid to recovering the indoor light into electric energy to supply energy for low-power consumption devices such as sensors, actuators, health care devices, portable electronics, sustainable smart housing, etc., fulfilling the self-energy supplier and wireless IoT system. [7] DSSCs operating under indoor light conditions have been termed as dye-sensitized indoor photovoltaics (DSiPVs); and the conversion efficiencies of DSiPVs are much higher than those of DSSCs under sun-light illumination. [8] One of the reasons for this is attributed to the narrower wavelength region of the indoor lights, including the light-emitting diode (LED), fluorescence lighting, and other artificial lights. Since the illumination light is low for indoor light, the conditions utilized to gain high cell efficiencies may differ from those for sunlight conditions. It has been found, for DSiPVs operating under dim light, that electrolytes prepared using a 3-methoxy propionitrile (MPN) solvent can get higher cell efficiencies than those using acetonitrile (ACN) solvent; this phenomenon is different from the solvent effect under sun-light illumination. [9,10] Furthermore, because a relatively small number of electrons are excited under room light conditions, lower concentrations of redox couple are required to recover the holes. The optimal redox for dim light operation is lower than that for sun-light environmental. [9][10][11] One of the other factors determining the performance of indoor To prepare bifacial dye-sensitized solar cells (DSSCs), the classical photoelectrode employing the main light-absorbing layer (ML) and scattering layer (SL) will encounter the scattering effect of SL to the rear-side incident light and, thereby, decrease the rear-side efficiencies. To solve this problem, the SL has always been removed for the fabrication of bifacial cells. However, the front-side efficiency decreases without the SL. Here, a novel structure of a TiO 2 photoelectrode is developed for bifacial DSSCs to solve the contrary effect for cells with and without an SL, increasing both the front-side and rear-side efficiencies. This new structure is constructed by introducing an add...

Indoor Dye-Sensitized Solar Cells with Efficiencies Surpassing 26% Using Polymeric Counter Electrodes

“…Most recently, our group introduced a novel photoelectrode structure for room light bifacial cells to efficiently harvest front- and rear-side light illumination . This structure was created by introducing an additional main layer after the scattering layer of the classical photoelectrode structure, fabricating a main layer/scattering layer/main layer sandwich structure of the TiO 2 layer.…”

“…This structure was created by introducing an additional main layer after the scattering layer of the classical photoelectrode structure, fabricating a main layer/scattering layer/main layer sandwich structure of the TiO 2 layer. The bifacial cells using this Y123 dye-sensitized photoelectrode and Pt-counter electrode achieved high front- and rear-side efficiencies of 21.11 and 18.90% (efficiency ratio = 0.89), respectively, under room light illumination of 200 lx . To further increase the efficiency of the cells, the 90 nm thin PEDOT layer was utilized to prepare the counter electrode in this study (Figure a).…”

“…After preparing the compact TiO 2 layer, the main and scattering TiO 2 layers were formed by printing the TiO 2 pastes with particle sizes of 30 and 300 nm, respectively. The thicknesses of the TiO 2 films were 6 μm + 4 μm (classical photoanode); 2, 4, 6, and 8 μm (only main TiO 2 layer); and 4 μm + 3.5 μm and 4 μm (sandwich structure). , These TiO 2 layers were sintered at a high temperature. Finally, the post-treatment process was carried out by dipping the TiO 2 films in a TiCl 4 aqueous solution.…”

“…The thicknesses of the TiO 2 films were 6 μm + 4 μm (classical photoanode); 2, 4, 6, and 8 μm (only main TiO 2 layer); and 4 μm + 3.5 μm and 4 μm (sandwich structure). 65,66 These TiO 2 layers were sintered at a high temperature. Finally, the post-treatment process was carried out by dipping the TiO 2 films in a TiCl 4 aqueous solution.…”

“…65 Most recently, high conversion efficiencies of 21.11% (front-side) and 18.90% (rear-side), were obtained for the bifacial cells using the 10 μm thick Pt layer, a photoelectrode based on a sandwich structure, Y123 dye, and a cobalt redox system under 200 lx fluorescent lighting. 66 In the present study, we aim at enhancing the front-side and rear-side efficiencies and efficiency ratios of the bifacial cells by the utilization of polymeric CEs.…”